<template>
  <div>
    <router-link
      tag="div"
      to='/'
      class="header-abs"
      v-show="showABs"
    >
      <div class="iconfont header-abs-back">&#xe624;</div>
    </router-link>
    <div
      class="header-fixed"
      v-show="!showABs"
      :style="opacityStyle"
    >
      景点详情
      <router-link to="/">
      <div class="iconfont header-fixed-back">&#xe624;</div>
      </router-link>
    </div>
  </div>
</template>

<script>
export default {
  name: 'DetailHeader',
  data () {
    return {
      showABs: true,
      opacityStyle: {
        opacity: 0
      }
    }
  },
  methods: {
    handleScroll () {
      const top = document.documentElement.scrollTop
      if (top > 60 && top < 140) {
        let opacity = top / 140
        opacity = opacity > 1 ? 1 : opacity
        this.opacityStyle = { opacity }
        this.showABs = false
      } else {
        this.showABs = true
      }
    }
  },
  // keepalive使用之后才有这个生命周期钩子
  activated () {
    window.addEventListener('scroll', this.handleScroll)
  },
  // 页面隐藏时执行 scroll全局事件解绑
  deactivated () {
    window.removeEventListener('scroll', this.handleScroll)
  }
}
</script>

<style lang="stylus" scoped>
  @import '~styles/varibles.styl'
    .header-abs
      position: absolute
      left: .2rem
      top: .2rem
      width: .8rem
      height: .8rem
      line-height: .8rem
      border-radius: .4rem
      text-align: center
      background: rgba(0, 0, 0, .8)
      .header-abs-back
        color: #fff
        font-size: .4rem
    .header-fixed
      z-index: 2
      position: fixed
      top: 0
      left: 0
      right: 0
      height: $headerHeight
      line-height: $headerHeight
      text-align: center
      color: #fff
      background: $bgColor
      font-size: .32rem
      .header-fixed-back
        position: absolute
        top: 0
        left: 0
        width: .64rem
        text-align: center
        font-size: .4rem
        color: #fff

</style>
